1. Field of the Invention
The present invention relates to a rotation detecting device and an anti-skid braking system utilizing such rotation detecting device.
2. Description of the Prior Art
It is well known that an electric generator is often used as a rotation detecting device used in an anti-skid braking system for automotive vehicles. This type of the electric generator generally includes a rotor mounted on an inner race of a wheel support bearing assembly, that is a rotatable member, and a stator mounted on an outer race of the wheel support bearing assembly that is a non-rotatable member, and is utilized to detect the number of revolutions, i.e., the rotational speed of the rotatable member in terms of the voltage level of an electric voltage signal generated by the electric generator.
It has, however, been found that the system in which the electric voltage signal generated by the electric generator is utilized to detect the rotational speed of the vehicle wheel is incapable of detecting the rotational speed of the vehicle wheel particularly at an extremely low speed rotation of the vehicle wheel at which the rotational speed of the vehicle wheel is barely zero and, hence, the power output from the electric generator is feeble or barely zero.